Advances in semiconductor processing continue, resulting in further reductions in minimum feature sizes and process scaling. As the semiconductor process nodes advance to smaller minimum feature sizes, for example, of 28 nanometers, 22 nanometers, and below, the areas available for contact plugs on device features such as gates and the respective substrate are reduced. In addition, as materials used in semiconductor processes advance, additional impacts on contact resistance due to the use of these advanced materials are observed. Accordingly, the approaches for reducing the respective impact are being researched.
Contact plugs are used to form the vertical electrical connections between a conductor layer such as a first level metal (known as M1), and a substrate region or a gate region formed below that level in an integrated circuit structure. Commonly used contact plugs include tungsten plugs.